The present inventions two terminal variable resistor increases its power-handling-capacity during a decrease in its numerical ohm value, contrary to present potentiometers or rheostats, that decrease their power capability with decreasing numerical ohm values. Related art three terminal potentiometers or rheostats have two fixed terminals and a wiper terminal. When moving the wiper terminal towards lower resistance the wiper is approaching one of the fixed end terminals, and less and less resistive material is available between the wiper and the end terminal. As an example a 200 ohm potentiometer used on 12 volts is safe as long as its wiper position is in the 100 or 50 ohm position, but when the wiper is in the 12 ohm position Ohm's law states: volts divided by ohms=amps(1 amp×12 volts=12 watts). Most related art 2 watt or 5 watt potentiometers would be burned out by this time unless a safety resistor is added in series, that I have had to do before I came up with this invention.
The potentiometer with the safety resistor of course prevents the usage of varying the resistance down to lower readings; a definite disadvantage.
Another options to present day engineers are to buy and use a much larger and more expensive rheostat, but even so, if the rheostat in this example was turned to 3 ohm the wattage would be 48 watts. The above limitations of related art potentiometers are described when varying current in a DC circuit, but if it is used for AC operation, other restrictions such as peak voltage versus R.M.S. voltage have to also be considered.
The above stated shortcomings of present day potentiometers or rheostats are similar if either a rotary or a linear slide-type potentiometer is used. The linear type is also a 3 terminal device with two fixed terminals and a wiper manipulated by a sliding handle, with the same inherent problems as above.